Generally, an optical filament is a substantially non-diffracting extremely intense optical feature within an optical beam that can propagate over relatively long distances through a medium. For example, when a beam of relatively high intensity light passes through a gas, the gas reacts and the beam of light begins to self-focus. The beam may focus such that the optical intensity increases significantly and the gas thereby ionizes to form plasma. The resulting plasma tends to defocus the beam. By balancing self-focusing with the defocusing effects of the plasma, one can generate an optical filament that propagates over greater distances.
Optical filaments have applications that may include laser controlled energy discharges, long-range deposition of high laser intensities, and Light Detecting and Ranging (LIDAR). The precise formation of optical filaments, however, is generally uncontrolled. That is, while an optical filament may be generated within a beam cross-section of a laser pulse, the placement of that optical filament within the beam cross-section is generally arbitrary. Optical filaments may generate significant plasma densities having lifetimes that far exceed the optical filament pulse lengths (i.e., durations). The plasma that is left in the wake of an optical filament is generally referred to herein as a plasma filament.